A video signal of video captured by a video camera is transmitted to a device (such as a switcher) through a transmission cable. Because it is difficult to transmit the electric signal without attenuation when the device is positioned remote from the video camera, a camera adaptor provided to the video camera converts the electric signal into an optical signal, and transmits the converted optical signal through an optical transmission cable. Then, a base station positioned remote from the video camera converts the optical signal into an electric signal. As above, long distance transmission is conducted.